Pipette apparatus



1965 R. A. ROBINSON 3,203,251

PIPETTE APPARATUS Filed March 19, 1963 INVENIOR ROBERT A. ROBINSON WWWATTORNEYS .used with less skilled personnel.

3,203,251 PIPETTE APPARATUS Robert Alexander Robinson, Cupertino,Calif., assignor to Beckman Instruments, Inc., a corporation ofCalifornia Filed Mar. 19, 1963, Ser. No. 266,389 5 Claims. (Cl.7342'5.6)

This invention relates to an improved precision pipette of a .type, forexample, as shown in United States Patent 2,974,528. Precision pipettesare employed for measuring and dispensing accurate volumes of fluid. Onetype of pipette includes a hollow, generally cylindrical, body portionwhich holds the major portion of the precise volume to be dispensed. Thebody portion terminates in capillary passages, the volume within thepipette being determined by the meniscuses formed at the capillary ends.

Pipettes of the above character are not infrequently mounted uponsqueeze bottles which form a reservoir for holding liquid sample. Bysqueezing the bottle the pipette is loaded with an exact volume ofliquid sample. Air valves have been provided so that when the bottle isreleased, air enters the reservoir from the surrounds to allow theliquid in the pipette to remain. Then, by squeezing the bottle andholding closed the valve means, the pipette dispenses its contents.

Pipette apparatus of the foregoing kind in general has been quitesatisfactory. However, it is a continuing objective in manufacture ofapparatus of this kind to make it as simple to manipulate as is possibleso that it can be Furthermore, it is an objective to minimize themanufacturing cost of apparatus of this kind.

In certain prior pipette structures liquid sample has been free toescape the container via the air valve. While in some instances this isnot particularly harmful, it will be evident that it is undesirable tomanipulate the air valve with a finger when corrosive or harmful liquidsamples are being handled.

Accordingly, in general it is an object of the present invention toprovide an improved micro-pipette apparatus.

It is a more specific object of the present invention to provide a moreeasily manipulated pipette apparatus.

Still another object of the invention is to provide an extremelysimplified pipette apparatus utilizing an air valve of capillarydimensions which permits air to flow into the reservoir while preventingliquid flow through same.

These and other objects of the invention will be more readily apparentfrom the following detailed description and drawing of a preferredembodiment thereof.

In the drawings:

FIGURE 1 shows a side elevation section view of pipette apparatusaccording to the invention.

FIGURE 1A is a detail view of the portion 1A-1A of FIGURE 1.

FIGURE 2 shows a side elevation view partially in section of a pipettewhich can be utilized in the structure shown in FIGURE 1.

FIGURES 3 through 5 diagrammatically represent the manipulation ofpipette apparatus according to the invention.

In general, a pipette assembly is provided for delivering a measuredvolume of liquid from a deformable reservoir which holds liquid sample.A dome closes the reservoir and supports a micro-pipette. The pipetteincludes a generally cylindrically-shaped hollow body portion, andcapillary passages at each end. One of the capillary passages extendsinto the dome in fluid communication therewith. In order to simplifymanipulation of the pipette apparatus, there is provided a vent of JUnited States Patent capillary dimensions in the dome to permitfluid-flow therethrough of air while precluding fluid-flow there-.through of liquid. The open end of the pipette which extends into thedome is dimensioned to provide less resistance to liquid flowtherethrough under pressure within said dome than is provided by thevent.

Referring to the drawing, a reservoir, such as the deformable flask orbottle 10 of suitable material, such as polyethylene supports a domeassembly 11. Assembly 11 comprises a generally cup-shaped dome 12,pipette 13, and retaining ring 14. Dome 12 forms a closure for reservoir10.

Means for mounting pipette 13 in dome 12 includes the opening 15 formedwith a flat surface 16 around the outer end thereof.

While various pipettes can be utilized in accordance with the invention,a preferred pipette is shown in FIG URE 2. Pipette 13 includes a singlecontinuous integral interior surface 17 bounded at each end by capillarypassages 18 and 19. Between passages 18, 19 a body portion 20 isdisposed having a relatively large volume. A molded ferrule 21 is formedto include a conicallyshaped surface 22, an annular groove 23 togetherwith a collar 24. Between groove 23 and collar 24 is a shoulder 25which, when installed, abuts surface 16.

Vent means of capillary dimension which will admit air under atmosphericpressure into the reservoir while precluding the escape of liquid isprovided near the top from within dome 12 than is true of vent 26.Passage 18 must, however, remain sufficiently small to form theretaining meniscus necessary to precision pipettes as refered to herein.Accordingly, in the above example, the diameter of passages 18, 19 wason the order of .015 and .003 inch, respectively.

As mentioned above, it is an objective of the present invention toprovide a pipette apparatus requiring as little manipulative skill aspossible. Accordingly, using the present arrangement in one procedureknown as reagent pipetting, the assembly is tipped, dome down, as shownin FIGURE 3 so as to fill the dome with liquid sample. Slight pressureis exerted on the sides of the bottle by squeezing, thereby filling thepipette until drops of liquid sample leave the tip. The bottle is thenturned upright, and the pressure released. Air enters via vent 26.Liquid sample is there-fore not withdrawn from pipette 13. Any dropremaining at either tip of pipette 13 can be shaken off or wiped off soas to provide precise volume of liquid sample. Subsequently, the pipettecontents are expelled by squeezing the bottle sufficiently to build upmore air pressure in dome 12 than vent 26 can release.

In the procedure known as transfer pipetting wherein liquid sample is tobe withdrawn from a test tube, as shown in FIGURE 5, and expelled intoanother container, the tip of the pipette is inserted into liquid sampleas contained in a test tube 27. The bottle is squeezed very lightly, andreleased. The pipette will fill slowly and possibly slightly overflowinto the reservoir 10. Tapping lightly removes any drop from either tipof the pipette. Transfer of the liquid sample is then effected bysqueezing the bottle to discharge the pipette contents as desired.

From the foregoing it will be evident that the above described pipetteassembly provides extremely simple operation utilizing a minimum of handmovements and manipulation. It will further be apparent that there areno valve manipulations or moving parts involved in the above structure.Furthermore, it will be appreciated that harmful or corrosive liquidscannot escape from the reservoir except through the tip of the pipette.

I claim:

1. A pipette assembly for delivering a measured volume of liquidcomprising a deformable reservoir for holding liquid contents to bedelivered, a cup-shaped dome, means retaining said dome to form aclosure for said reservoir, a vent consisting of a single hole extendingthrough the wall of said dome, a micro-pipette having acylindrically-shaped hollow body portion, capillary passages formed ateach end of said body portion to retain for delivery a precise volume ofliquid defined between meniscuses formed within each said capillarypassage, means for mounting said body portion with one of said passagesextending into said dome in fluid communication with the interiorthereof, the last said passage providing an opening dimensioned toprovide less resistance to liquid flow therethrough under pressure fromwithin said dome when the assembly is inverted for filling than providedby said vent, said pipette offering more resistance to gas flowtherethrough into said dome when the pipette is filled with liquid anddisposed upright than the gas flow resistance of said vent at such time.

2. Pipette apparatus as defined in claim 1 wherein said vent has adiameter on the order of .005 inch, the capillary passage within saiddome has a diameter on the order of .015 inch, and the other capillarypassage has a diameter on the order of .003 inch.

3. Pipette apparatus as defined in claim 1 wherein the ratio of thediameter of said vent to the diameter of the opening in the passagewithin the dome is 1 to 3.

4. In pipette apparatus for delivering a measured volume of liquid andhaving a deformable reservoir for holding liquid to be delivered, a domeassembly comprising a cup-shaped dome, means retaining said dome to forma closure for said reservoir, a vent consisting of a single holeextending through the wall of said dome, a micropipette having acylindrically-shaped hollow body portion, capillary passages formed ateach end of said body portion to retain for delivery a precise volume ofliquid defined between meniscuses formed Within each said capillarypassage, means for mounting said body portion with one of said passagesextending into said dome in fluid communication with the interior of thedome, the

inner end of said vent and of said pipette being disposed and exposed tobe submerged in liquid whenever the apparatus is inverted to permit thepipette to be filled during such inversion by applying pressure build-upwithin the dome, said vent being dimensioned to preclude liquid flowtherefrom prior to emergence of flow through the pipette when the outerend of the latter is held below the vent, the inner capillary passageproviding an opening dimensioned to oifer less resistance to liquid fiowtherethrough under pressure from within the dome when the apparatus isinverted than offered by said vent at such time, the other capillarypassage being formed and dimensioned to provide greater resistance togas flow through the pipette into the dome when the pipette is filledwith liquid and disposed upright than the gas flow resistance of thevent at such time.

5. A pipette assembly for delivering a measured volume of liquidcomprising a deformable reservoir for holding liquid contents to bedelivered, a cup-shaped dome, means retaining said dome to form aclosure for said reservoir, a vent consisting of a single hole extending through the wall of said dome, a micro-pipette having acylindrically-shaped hollow body portion, capillary passages formed ateach end of said body portion to retain for delivery a precise volume ofliquid defined between meniscuses formed within each said capillarypassage, means for mounting said body portion with one of said passagesextending into said dome in fluid communication with the interiorthereof, the inner end of said hole and of said one of said passagesboth being disposed and exposed to be submerged in the liquid contentsfrom the reservoir upon inversion of the assembly for filling saidpipette when the assembly is inverted, the openings of said vent andpipette being dimensioned with respect to each other to pass liquid intosaid pipette in preference to passing liquid through the vent when theapparatus is inverted for filling, and when the pipette is filled andthe apparatus disposed upright to pass air into the dome via the vent inpreference to entry of gas into the dome via the pipette.

References Cited by the Examiner UNITED STATES PATENTS 1,459,282 6/23Clark 222-209 1,715,429 6/29 Saugman.

2,237,213 4/44 Brown 73425.6 3,118,306 1/64 Sanz 73425.4

RICHARD C. QUEISSER, Primary Examiner.

1. A PIPETTE ASSEMBLY FOR DELIVERING A MEASURED VOLUME OF LIQUIDCOMPRISING A DEFORMABLE RESERVOIR FOR HOLDING LIQUID CONTENTS TO BEDELIVERED, A CUP-SHAPED DOME, MEANS RETAINING SAID DOME TO FORM ACLOSURE FOR SAID RESERVOIR, A VENT CONSISTING OF A SINGLE HOLE EXTENDINGTHROUGH THE WALL OF SAID DOME, A MICRI-PIPETTE HAVING ACYLINDRICALLY-SHAPED HOLLOW BODY PORTION, CAPILLARY PASSAGES FORMED ATEACH END OF SAID BODY PORTION TO RETAIN FOR DELIVERY A PRECISE VOLUME OFLIQUID DEFINED BETWEEN MENISCUSES FORMED WITHIN EACH SAID CAPILLARYPASSAGE, MEANS FOR MOUNTING SAID BODY PORTION WITH ONE OF SAID PASSAGESEXTENDING INTO SAID DOME IN FLUID COMMUNICATION WITH THE INTERIORTHEREOF, THE LAST SAID PASSAGE PROVIDING AN OPENING DIMENSIONED TOPROVIDE LESS RESISTANCE TO LIQUID FLOW THERETHROUGH UNDER PRESSURE FROMWITHIN SAID DOME WHEN THE ASSEMBLY IS INVERTED FOR FILLING THAN PROVIDEDBY SAID VENT, SAID PIPETTE OFFERING MORE RESISTANCE TO GAS FLOWTHERETHROUGH INTO SAID DOME WHEN THE PIPETTE IS FILLED WITH LIQUID ANDDISPOSED UPRIGHT THAN THE GAS FLOW RESISTANCE OF SAID VENT AT SUCH TIME.